The present invention relates to large diameter seals and, more particularly, to large diameter seals having thin, pliable coatings on their outside diameters, and methods of making such seals. In general, this process can be performed on any so-called assembled seal.
Ordinary oil seals of from, perhaps, one inch to six inches in diameter, are made from a rigid casing and have bonded rubber lips of various kinds. Such seals are usually produced by compression molding, transfer molding or injection molding the rubber portion onto a steel, aluminum or like casing. Large diameter seals, for example, those of eight inches to sixty inches or more in diameter, are far too big to be economically manufactured by such a molding process. In other words, trying to inject rubber in a mold having an inside diameter of at least eight inches, but usually 12 inches up to 60 inches or more in diameter, would be very awkward, expensive, and impractical. To make such a mold would be extremely costly, especially considering that the mold would ordinarily be very seldom used.
In a regular or small diameter oil seal, the casing is made from a stamping or drawing. Such seals have either a metal or rubber OD (“outside diameter”). However, a large diameter seal is customarily made by a different method, with such method involving forming the casing in one step by a spinning operation, wherein the two radial flanges surround a major or axial portion of the casing. Thus, the casing is formed by placing a ring of metal in a spinning apparatus and spinning or bending the flanges thereon to form a generally U-shaped casing, as is well known in the art.
Thereafter, a portion of the elastomeric seal body is formed separately, cut into whatever overall length is desired, the end portions are bonded to each other to create a closed loop, and thereafter, the elastomeric portion is placed within the casing, and secured thereto by clinching. The resulting seal, which may be made with or without a garter spring, or in some cases with an embedded garter spring, is then ready to be used.
However, the present invention uses a different method. The seal is desired to have a rubber outside diameter (OD), for several important reasons. Installing a large diameter seal in a seal-receiving area, customarily a counterbore on a large machine such as a the rollers in a paper mill, steel mill or some other such application, because of the size of the seal, is customarily difficult. When the seal is even slightly too small for the application, it allows leakage between the counterbore and the OD of the casing. This is also the case with irregularities in the surface. If the seal is too large, the seal is unable to be installed, because the line-to-line contact necessary is extremely difficult to obtain. It is customary for such a large diameter seal-receiving area to be required to be free from nicks, scratches or the like, and as a result, installing such seals correctly becomes a major operation, particularly if the machine on which it is to be installed is old or has suffered from lack of maintenance.
Consequently, there has been a desire to manufacture a large diameter seal which would enable the secondary seal or the outside diameter of the seal to the counterbore to be completely and effectively sealed. Such a seal would also require a chamfer on at least one surface of its outside diameter, in addition preferably to being made from an elastomeric material which would be able to accommodate a slight out-of-round condition or other irregularities in the seal-receiving counterbore.
Accordingly, it is an object of the present invention to provide an improved large diameter seal.
Another object is to produce a large diameter seal, which includes a band of elastomeric material on its outside diameter.
Another object is to provide a method of creating an outside diameter rubber seal without creating a large-diameter mold, and which would not require equipment other than that required to make the remainder of the seal itself.
A still further object would be to provide a seal which would accommodate small imperfections in the installed or outside diameter, including an out-of-round condition or having nicks or other irregularities in the OD.
A still further object is to provide a method which involves creating an elastomeric seal band by bonding the end portions of a continuous strip of thin, elastomeric material into a closed loop, placing a bonding adhesive on the casing, and thereafter stretching the rubber band thus made into a larger diameter, allowing it to spring back and cling to the outside diameter of the casing, and then trimming one or both edges to provide a chamfer to accommodate and simplify the installation of such a seal.
A further object of the invention is to provide a rubber OD on a seal which would thereafter allow for improved ease of installation and removal, and would not damage the customer's hardware.
An object of the invention is to develop a rubber material for the OD of a seal which allows a certain amount of compression set during installation but thereafter remains resilient indefinitely.
Another object would be to provide an improved, rubber outside diameter seal which is especially useful in steel production, mining, pulp and paper and other industries generally requiring large diameter seals.
A still further object would be to provide a large diameter seal having a greatly reduced press-in or installing force, and a reduced extraction force.
A related object is to provide a seal which can be reinstalled without leaking in the application after removal from the counterbore.
Another object is to provide a seal which could compensate for an out-of-round or worn condition of the counterbore in which it is received.
A further object is to provide a seal which will not cause any damage to its associated counterbore, even during extraction.
A still further object is to provide a seal which has an outside diameter lead-in chamfer or radius.